Columba in the context of "Hiberno-Scottish mission"

Christianity has been the largest religion in Ireland since the 5th century. After a pagan past of Antiquity, missionaries (most famously including Saint Patrick) converted the Irish tribes to Christianity in quick order. This produced a great number of saints in the Early Middle Ages, as well as a faith interwoven with Irish identity for centuries since − though less so in recent times.

Most Christian churches are organized on an "all-Ireland" basis, including both the Republic of Ireland and Northern Ireland. In the 2022 census, 76.1% of residents in the Republic of Ireland identified as Christians: 69.1% as Catholics, 4.2% as Protestants, 2.1% as Orthodox Christians and 0.7% as other Christians. In the 2021 Northern Irish census, 79.7% of residents identified as Christians: 42.3% as Catholics, 16.6% as Prebysterian, 11.5% as Church of Ireland members, 2.4% as Methodist and 6.9% as other Christians. Orthodoxy has been the fastest growing branch of Christianity in Ireland since 1991.

The Picts were a group of peoples in what is now Scotland north of the Firth of Forth, in the Early Middle Ages. Where they lived and details of their culture can be gleaned from early medieval texts and Pictish stones. The name Picti appears in written records as an exonym from the late third century AD. They are assumed to have been descendants of the Caledonii and other northern Iron Age tribes. Their territory is referred to as "Pictland" by modern historians. Initially made up of several chiefdoms, it came to be dominated by the Pictish kingdom of Fortriu from the seventh century. During this Verturian hegemony, Picti was adopted as an endonym. This lasted around 160 years until the Pictish kingdom merged with that of Dál Riata to form the Kingdom of Alba, ruled by the House of Alpin. The concept of "Pictish kingship" continued for a few decades until it was abandoned during the reign of Caustantín mac Áeda.

Pictish society was typical of many early medieval societies in northern Europe and had parallels with neighbouring groups. Archaeology gives some impression of their culture. Medieval sources report the existence of a Pictish language, and evidence shows that it was an Insular Celtic language related to the Brittonic spoken by the Celtic Britons to the south. Pictish was gradually displaced by Middle Gaelic as part of the wider Gaelicisation from the late ninth century. Much of their history is known from outside sources, including Bede, hagiographies of saints such as that of Columba by Adomnán, and the Irish annals.

The Book of Kells (Latin: Codex Cenannensis; Irish: Leabhar Cheanannais; Dublin, Trinity College Library, MS A. I. [58], sometimes known as the Book of Columba) is an illustrated manuscript and Celtic Gospel book in Latin, containing the four Gospels of the New Testament together with various prefatory texts and tables. It was created in a Columban monastery in either Ireland or Scotland, and may have had contributions from various Columban institutions from each of these areas. It is believed to have been created c. 800 AD. The text of the Gospels is largely drawn from the Vulgate, although it also includes several passages drawn from the earlier versions of the Bible known as the Vetus Latina. It is regarded as a masterwork of Western calligraphy and the pinnacle of Insular illumination. The manuscript takes its name from the Abbey of Kells, County Meath, which was its home for centuries.

The illustrations and ornamentation of the Book of Kells surpass those of other Insular Gospel books in extravagance and complexity. The decoration combines traditional Christian iconography with the ornate swirling motifs typical of Insular art. Figures of humans, animals and mythical beasts, together with Celtic knots and interlacing patterns in vibrant colours, enliven the manuscript's pages. Many of these minor decorative elements are imbued with Christian symbolism and so further emphasise the themes of the major illustrations.

Saint Patrick (Latin: Pātricius; Irish: Pádraig Irish pronunciation: [ˈpˠɑːɾˠɪɟ] or Irish pronunciation: [ˈpˠaːd̪ˠɾˠəɟ]; Welsh: Padrig) was a fifth-century Romano-British Christian missionary and bishop in Ireland. Known as the "Apostle of Ireland", he is the primary patron saint of Ireland, the other patron saints being Brigid of Kildare and Columba. He is also the patron saint of Nigeria. Patrick was never formally canonised by the Catholic Church, having lived before the current laws were established for such matters. He is venerated as a saint in the Catholic Church, the Lutheran Church, the Church of Ireland (part of the Anglican Communion), and in the Eastern Orthodox Church, where he is regarded as equal-to-the-apostles and Enlightener of Ireland.

The dates of Patrick's life cannot be fixed with certainty, but there is general agreement that he was active as a missionary in Ireland during the fifth century. A recent biography on Patrick shows a late fourth-century date for the saint is possible. According to tradition dating from the early Middle Ages, Patrick was the first bishop of Armagh and Primate of Ireland, and is credited with bringing Christianity to Ireland (despite evidence of some earlier Christian presence on the island), and converting Ireland from paganism in the process.

Saint Brigid of Kildare or Saint Brigid of Ireland (Irish: Naomh Bríd; Classical Irish: Brighid; Latin: Brigida; c. 451 – c. 525) is the patroness saint (or 'mother saint') of Ireland, and one of its three national saints along with Patrick and Columba. According to medieval Irish hagiographies, she was an abbess who founded the important abbey of Kildare (Cill Dara), as well as several other convents of nuns. There are few documented historical facts about her, and her hagiographies are mainly anecdotes and miracle tales, some of which are rooted in pagan folklore. They say Brigid was the daughter of an Irish clan chief and an enslaved Christian woman, and was fostered in a druid's household before becoming a consecrated virgin. She is patroness of many things, including poetry, learning, healing, protection, blacksmithing, livestock, and dairy production. In her honour, a perpetual fire was kept burning at Kildare for centuries.

Some historians suggest that Brigid is a Christianisation of the Celtic goddess Brigid. The saint's feast day is 1 February, and traditionally it involves weaving Brigid's crosses and many other folk customs. It was originally a pre-Christian festival called Imbolc, marking the beginning of spring. Since 2023, it has been a public holiday in the Republic of Ireland. This feast day is shared by Dar Lugdach, who tradition says was her student, close companion, and successor.

Iona (/aɪˈoʊnə/; Scottish Gaelic: Ì Chaluim Chille [ˈiː ˈxal̪ˠɪm ˈçiʎə] , sometimes simply Ì) is an island in the Inner Hebrides, off the Ross of Mull on the western coast of Scotland. It is mainly known for Iona Abbey, though there are other buildings on the island. Iona Abbey was a centre of Gaelic monasticism for three centuries and is today known for its relative tranquility and natural environment. It is a tourist destination and a place for spiritual retreats. Its modern Scottish Gaelic name means "Iona of (Saint) Columba" (formerly anglicised as "Icolmkill").

Iona's resident population is about 180. In March 1980, the Hugh Fraser Foundation donated much of the main island (and its off-lying islands) to the current owner, the National Trust for Scotland. The abbey and some church buildings are owned by the Iona Cathedral Trust.

Derry, officially Londonderry, is the second-largest city in Northern Ireland. Located in County Londonderry, the city now covers both banks of the River Foyle. Cityside and the old walled city being on the west bank and Waterside on the east, with two road bridges and one footbridge crossing the river in-between.

The population of the city was 85,279 in the 2021 census, while the Derry Urban Area had a population of 105,066 in 2011. The district administered by Derry City and Strabane District Council contains both Londonderry Port and City of Derry Airport. Derry is close to the border with County Donegal, with which it has had a close link for many centuries. The person traditionally seen as the founder of the original Derry is Saint Colmcille, a holy man from Tír Chonaill, the old name for almost all of modern County Donegal, of which the west bank of the Foyle was a part before 1610.